In recent years, there has been widely used a key-less entry system in which it is possible to carry out locking and unlocking of a door of a vehicle or the like without key operation. In many such key-less entry systems, there is employed a constitution provided with an electrostatic capacitance type touch sensor inside the door handle in order to detect a user's contact with a door handle.
In such an electrostatic capacitance type touch sensor, the floating capacitance of the sensor electrode on the inside is measured. This floating capacitance increases by the user's contact with the door handle. Then, in the electrostatic capacitance type touch sensor, it is constituted such that the user's contact with the door handle is detected in a case in which the measurement value of the floating capacitance of the sensor electrode becomes a predetermined value or more.
However, in the rainy weather, rainwater which is a conductor accumulates in the vicinity of the sensor electrode, so that the floating capacitance of the sensor electrode increases. For this reason, regardless of the fact that the user did not contact the door handle, it sometimes happened that lock or unlock was carried out by an erroneous detection that the user would contact the door handle.
Here, the vicinity of the sensor electrode where rainwater easily accumulates means a boundary portion between the upper surface of the door handle and the door panel. Focusing attention on this fact, there has been proposed a technology in which the contact detection sensitivity of the sensor electrode at a portion near to the door panel is made lower than the contact detection sensitivity of the sensor electrode at a portion far from the door panel (see Patent Document 1: hereinafter, referred to as “conventional example”). In the technology of this conventional example, it is configured such that a constitution is employed in which a notch portion is formed at a portion of the sensor electrode near to the door panel and the housing of the door handle which houses the electrostatic capacitance type touch sensor employs a constitution in which in the vicinity of the sensor electrode, the dielectric constant of a portion far from the door panel exceeds the dielectric constant of a portion near to door panel.